1. Field of the Invention
The present invention relates to an image processing system, an image processing method, a memory card and a storage medium, and more particularly to an image processing system and method capable of improving the reliability of image file data by using a digital signature.
2. Related Background Art
In image processing systems and methods practically used nowadays, data generated by a personal computer (hereinafter, abbreviated as PC), an electronic pocketbook, a digital camera or the like is once transferred to and stored in a storage medium and thereafter, the storage medium is connected to an image control device to facilitate printing.
Such data includes output image file data as well as a property file describing which image is output in accordance with what output specifications.
FIG. 6 is a block diagram of an image processing system disclosed in Japanese Patent Application Laid-open No. 10-226117.
This image processing system has an image input/output unit (main) body 61, an image input/output control device 62, an image input/output instruction key 63, a memory card I/F unit 64 and a memory card 65.
The image input/output control device 62 reads image file data and a property file from the memory card 65 in order to execute an image output process. The property file is included in the image file data and describes what data is to be transferred to the image input/output unit body 61 in accordance with what output specifications to form an image.
Such a conventional image output method is, however, associated with a problem that even if image file data stored in a memory card is altered or forged, it is not possible to discriminate between original data and altered or forged data and to verify the image file data.
Another problem is that if a third party has the memory card, data in this card may be used illegally. Namely, the problem is a lack of security of data in the memory card and inability to guarantee data reliability.
By storing property information designating an image output format in a memory card, an image in a format intended by a distributor (writer) can be supplied. Such format includes, for example, to record which image or images are recorded on a single sheet, to output an image at each designated resolution, to combine an additional image representative of an image proprietor, and the like. However, in this case, if data is altered, the format intended by the distributor cannot be supplied.
This may pose another problem if a copyrighted image is to be distributed.
On the image reception side, an image not guaranteed as genuine may be output.